The present invention relates to an impulse response setting method for the 2-channel echo canceling filter, a two-channel echo canceller, and a two-way 2-channel voice transmission device. More particularly, this invention relates to solve the coefficient indefiniteness problem in the 2-channel echo canceling process.
In the two-way 2-channel audio transmission used for the videoconference system or the like, a coefficient indefiniteness in the echo canceller has been pointed out. Various solutions to the problem have been proposed (The Journal of the Institute of Electronics, Information and Communication Engineers, Vol. 81, No. 3 P. 26 to 274 1998, March). One of the solutions is to reduce an interchannel correlation. Techniques to reduce the interchannel correlation are, for example, addition of random noise, elimination of correlation by the filter, interchannel frequency shift, use of interleave comb filter, and nonlinear processing (Japanese patent laid-open No. 190848/1998). Another solution is to utilize the fact that the interchannel correlation function delicately varies by a spatial movement of a sound source in an actual acoustic field (Japanese patent laid-open No. 93680/1998).